/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.messaging.simp;

import org.springframework.beans.factory.ObjectFactory;
import org.springframework.beans.factory.config.Scope;
import org.springframework.lang.Nullable;

/**
 * A {@link Scope} implementation exposing the attributes of a SiMP session
 * (e.g. WebSocket session).
 *
 * <p>Relies on a thread-bound {@link SimpAttributes} instance exported by
 * {@link org.springframework.messaging.simp.annotation.support.SimpAnnotationMethodMessageHandler}.
 *
 * @author Rossen Stoyanchev
 * @since 4.1
 */
public class SimpSessionScope implements Scope {

    @Override
    public Object get(String name, ObjectFactory<?> objectFactory) {
        SimpAttributes simpAttributes = SimpAttributesContextHolder.currentAttributes();
        Object scopedObject = simpAttributes.getAttribute(name);
        if (scopedObject != null) {
            return scopedObject;
        }
        synchronized (simpAttributes.getSessionMutex()) {
            scopedObject = simpAttributes.getAttribute(name);
            if (scopedObject == null) {
                scopedObject = objectFactory.getObject();
                simpAttributes.setAttribute(name, scopedObject);
            }
            return scopedObject;
        }
    }

    @Override
    @Nullable
    public Object remove(String name) {
        SimpAttributes simpAttributes = SimpAttributesContextHolder.currentAttributes();
        synchronized (simpAttributes.getSessionMutex()) {
            Object value = simpAttributes.getAttribute(name);
            if (value != null) {
                simpAttributes.removeAttribute(name);
                return value;
            } else {
                return null;
            }
        }
    }

    @Override
    public void registerDestructionCallback(String name, Runnable callback) {
        SimpAttributesContextHolder.currentAttributes().registerDestructionCallback(name, callback);
    }

    @Override
    @Nullable
    public Object resolveContextualObject(String key) {
        return null;
    }

    @Override
    public String getConversationId() {
        return SimpAttributesContextHolder.currentAttributes().getSessionId();
    }

}
